Assessment of linguistic and cognitive abilities in the learning disabled deaf population

Abstract

This study set out to determine methods of identifying a specific subgroup of learning disabled deaf individuals - those with a language impairment. A South African Sign Language (SASL) test battery was developed for assessing sign language skills in the learning disabled deaf population, Linguistic and cognitive profiles for three learning disabled profoundly deaf adults and three nondisabled profoundly deaf adult controls was described. The battery of diagnostic tests consisted of a standard battery of language tests adapted for SASL, formal sign language tests, a signed narrative discourse task and a cognitive test battery translated into SASL. The inclusion of a signed narrative task and its analysis method enabled an examination of higher order linguistic and cognitive skins and specific aspects of sign language which have not been previously investigated. The perception and production of facial expressions used for linguistic purposes in sign, the breakdown of this perception and production and the role of these facial expressions in the macrostructure of signed discourse were examined ill this study. Although much research on the production of facial expressions and other nonmanual behaviours in sign language has been undertaken previously. to the writer's best knowledge no research concerning the perception of facial expressions in sign language, the breakdown in the perception and use of facial expressions in sign language and its role in the form of evaluative elements in the macrostructure of signed discourse have been previously undertaken. Furthermore the function of facial expressions as grammatical markers in sign language and other functions of facial processing not particular to signed languages were studied from a neuropsychological perspective. Studying the breakdown of sign language from a psycholinguistic perspective allowed for the identification of some of the underlying processes essential to sign language competence. A fundamental component of this study was the involvement of adult deaf native signers at all levels of the research. The particular combination of tests used in this study revealed linguistic and cognitive deficits in the three learning disabled deaf (LDD) subjects which were not evident in the control subjects. It highlighted the similarities as well as the heterogeneity of the three LDD subjects' linguistic and cognitive profiles in terms of both the nature and degree of severity of the deficits. In addition it revealed deficits in some of the underlying processes in sign language, such as spatial and facial processing, as well as their manifestations in various forms. The numerous theoretical and clinical implications arising from the results of this study are discussed in detail.